Dados do Trabalho

Title

PREGNANCY RESULTS USING OOCYTES CRYOPRESERVED FOR FERTILITY PRESERVATION: A SINGLE CENTER’S EXPERIENCE

Objective

Most data in the literature deals with IVF cryopreserved surplus oocytes, and little information is available on pregnancy results when the indication is exclusively fertility preservation. Then, this study aims to evaluate the results of IVF cycles with oocytes cryopreserved with the objective of preserving fertility.

Methods

Retrospective study. Patients who underwent oocyte cryopreservation (OC) for fertility preservation and later thawed the oocytes for their own use by the end of 2022 were included. Therefore, patients who inseminated and cryopreserved parts of their oocytes were excluded. Laboratory results and cumulative pregnancy rates according to age at the time of cryopreservation and the number of cryopreserved oocytes were evaluated. Student's t, Chi-square and Fisher's exact tests were used for statistical analysis, considering p<0.05.

Results

The cryopreservation cycles occurred between 2004 and 2021, and the thawing cycles between 2010 and 2022. Oocytes from 46 patients, originating from 61 OC cycles (two slow freezing cycles and 59 vitrification cycles), were thawed which resulted in 50 cycles of IVF with fresh transfer (FOT) and eight cycles of cryopreserved embryo transfer (FET). The mean age of the patients at the time of cryopreservation was 37.5 ± 2.4 years, and at thawing, 40.7 ± 3.7 years. The total number of thawed oocytes was 382; the survival rate was 80.7% (n=308) and the fertilization rate was 79.2% (n=244). In 31 cycles, the embryo culture lasted 5 days and the blastulation rate was 40.7% (77/189). The cumulative rates were 48.9% for total pregnancy, 40,0% for clinical pregnancy, and 31,1% for birth/ongoing pregnancy, with 22.2% miscarriage. The cumulative clinical pregnancy rate was 60.0% when the age at cryopreservation was < 35 years (n=5), 47.6% when between 35-37 years (n=21), and 29.4% when between 38-40 years old (n=17); patients with >40 years (n=3) did not get pregnant (p=0.444). The cumulative clinical pregnancy rate was 45.8% when 4 to 9 eggs were frozen and 45.5% when 10 to 15 eggs were frozen; patients with <4 oocytes did not get pregnant. Four patients who did not become pregnant still have eight cryopreserved embryos.

Conclusion

The search for OC to preserve fertility has been growing, both in cancer patients and mainly, due to the delay of motherhood. In our experience, the number of procedures has quadrupled in the last decade, with a growth of 20% per year in the previous 5 years. However, the number of cases of patients who sought the clinic to try to conceive with their oocytes is still low. But, even so, these results suggest that patients can freeze their eggs even after 35 years old but before 40, and have more than three frozen eggs. This data shows the importance of offering patients such an opportunity.

Keywords

Oocyte; fertility preservation; pregnancy; female age.